N = int(input())
ccc = input()
R = ccc.count('R')
ans = 0
for i in range(R):
    if ccc[i] == 'W':
        ans += 1
print(ans) N = int(input()) N int(input()) int input() input ccc = input() ccc input() input R = ccc.count('R') R ccc.count('R') ccc.count ccc count 'R' ans = 0 ans 0 for i in range(R):
    if ccc[i] == 'W':
        ans += 1 i range(R) range R if ccc[i] == 'W':
        ans += 1 ccc[i] == 'W' ccc[i] ccc i 'W' ans += 1 ans 1 print(ans) print ans R = ccc.count('R') ccc.count('R') R ccc = input() input() ccc ans = 0 0 ans N = int(input()) int(input()) N ans += 1 1 ans
N = int(input())
ccc = input()
R = ccc.count('R')
ans = 0
for i in range(R):
    if ccc[i] == 'W':
        ans += 1
print(ans)
